Evaluation of rice blast resistance and detection of resistance genes of rice varieties in regional trials in the middle and lower reaches of Yangtze River

【Objective】To explore the blast resistance level of rice varieties tested in the middle and lower reaches of the Yangtze River and the effect of resistance gene aggregation on the resistance of rice blast and provide a theoretical basis for the approval of new varieties and the rational use of disease-resistant varieties.【Method】The artificial spray inoculation method was used to identify the rice blast resistance of the 252 varieties in regional trials in the middle and lower reaches of the Yangtze River from 2018 to 2020. Two sets of multiplex PCR systems（Pi1 and Pikh，Pi9 and Pik）were used to detect the resistance genes Pi9，Pik，Pi1 and Pikh in the tested rice varieties. The relationship between the aggregation mode of resistance genes and the resistance rate of rice blast was analyzed.【Result】The spike blast resistance rates of the tested materials from 2018 to 2020 were 47.0%，38.3% and 35.2%，respectively，which decreased year by year. 252 tested materials contained 0 to 4 tested resistance genes. There were 14 materials containing no tested resistance genes，accounting for 5.6%，and the spike blast resistance rate was 14.3%；63 materials contained 1 resistance gene，accounting for 25.0%，and the spike blast resistance rate was 11.1%；81 materials contained 2 resistance genes，accounting for 32.1%，and the spike blast resistance rate was 42.0%；81 materials contained 3 resistance genes，accounting for 32.1%，and the spike blast resistance rate was 65.4%；13 materials contained 4 resistance genes，accounting for 5.2%， and the spike blast resistance rate was 53.8%. In general，the spike blast resistance rate of the tested materials increased with the number of resistance genes，showing an upward trend. The rice blast resistance gene combinations Pi9+Pikh， Pi9+Pik+Pikh and Pi9+Pik+Pi1+Pikh were suitable resistance gene combinations in Anhui.【Conclusion】The resistance to blast disease of rice varieties tested in the middle and lower reaches of the Yangtze River from 2018 to 2020 is average. Multi-gene aggregation can improve rice blast resistance，but the appropriate combination of resistance genes should be selected instead of simply superposition.